If you bought the perpetual license version, the Stand Alone LR 6 (Not the subscription based version), LR Mobile is only a Trial. LR Mobile is only available with the subscription based LR CC 2015.
Thank you for your response.
Yes, I have bought the Stand Alone LR 6 product.
But maybe I have downloaded the LR 6.3 CC product a month ago as an free test/trial and now (yesterday actually) updated LR with the "Stand Alone LR 6" product (version 6.4)?
Can you guide me how to find the product version I'm running and if the licens (the LR serial number defined in my Adobe account) is in use for my present LR 6.4 product?
Go to the menu:
Help >> System Info
That will show you the installed version.
Okay, now I found the requested information.
Lightroom-version: 6.4 [ 1060496 ]
Operativsystem: Mac OS 10
Version: 10.11 
"Evig" stands for "ongoing".
Thank you very much for your support.